1. Field of the Invention
This invention relates to compounds containing the diimidazo [4,5-b:4',5'-e]pyrazine nucleus, a novel, tricyclic, heterocyclic ring system, and to their tetracarboxamidopyrazine precursors.
2. Description of the Prior Art
Compounds of the diimidazo [4,5-b:4',5'-e]pyrazine type have not been disclosed in the prior art. The closest disclosures are:
1. Schipper and Day, Elderfield's "Heterocyclic Compounds", Vol. 5, p. 274 (Wiley, 1957). Diacyl derivatives of o-phenylenediamine are converted to benzimidazole by heating in an atmosphere of nitrogen in accordance with the following equation: ##SPC3## PA1 2. Schipper and Day, J. Am. Chem. Soc., Vol. 74, p. 350 (1952). Reaction of 2,3 -diamino-5,6-dimethylpyrazine with excess carboxylic acid halides in boiling xylene gave 2-substituted 1H-imidazo-[4,5-b]pyrazines: ##SPC4##
Where R = alkyl or phenyl.